Many types of liquid spray nozzles are known prior to the present invention. Many of these nozzles which are capable of generating fine liquid droplets on the order of 300 micron diameter or smaller have points of high frictional wear. The points of high wear cannot be eliminated by prior designs but the effects of these wear points can be reduced by the use of specialized materials. Some prior nozzles are incapable of handling liquids which contain more than a small portion of solids. This is because certain prior nozzles rely on small orifices to produce fine atomization of the liquid and these small orifices will tend to plug if the liquid being sprayed includes particulate material. The need to spray liquids containing particulate material is particularly important in certain applications of spray nozzles such as where a source of highly filtered liquid is not available.
Spray nozzles which produced a hollow cone spray were known prior to the present invention and one example is shown in U.S. Pat. No. 3,680,781. Most hollow cone sprays have a tendency for the spray to collapse on itself due to the existence of a lower pressure within the hollow core of the cone as compared with the ambient pressure. Collapsing of the cone has an adverse effect on the penetration of the spray as well as the area of coverage of the spray pattern. The elimination of this collapsing would therefore be an advantage.
A further disadvantage of known apparatus is that it is difficult to make field modifications to the nozzle when a different spray pattern is desired or when repairs are necessary.
A primary application of nozzles of the present invention is for cooling hot gases in applications such as spray towers and thermal processing equipment such as rotary kilns. Since most of these installations do not always have a readily available source of clean water, the ability to spray unfiltered water and still maintain a droplet size distribution conductive to good evaporative cooling efficiency is of primary concern.
Also of importance in this type of application is the spray pattern. Since the spray nozzle is often located in a duct or other confined vessel, it is important that the spray pattern be sufficiently large to cover the area through which the gas passes but not so large as to spray the walls of the duct or vessel. Such a situation would result in liquid running down the walls which could produce a muddy condition rather than merely cooling the gases. It is therefore important to have a spray nozzle which can be easily modified in the field in the event field conditions are not the same as had been anticipated during design. It is also important to not have a spray pattern which tends to collapse on itself because such a situation reduces coverage and adversely affects the penetration of the spray.